Multiple traumas to the brain are the most common type of catastrophic injury and a leading cause of death in athletes. Multiple brain injuries may occur as the long-term disabilities resulting from a single mild traumatic brain injury (MTBI) are often overlooked and the most obvious clinical symptoms appear to resolve rapidly. Most previous research has: a) failed to provide pure pre-injury status of MBTI subjects which may lead to misdiagnosis of the persistent or new neurological and behavioral deficits following a single brain injury;b) focused primarily on transient deficits after single MTBI, and failed to examine long-term deficits and symptoms of multiple MTBI;c) focused primarily on pathophysiology, neurocognitive or behavioral sequelae of MTBI in isolation;and d) failed to identify and predict athletes at risk for traumatic brain injury. We will build on our previous work and plan to identify and examine both transient and long-term behavioral, sensory-motor, neuropsychological, and neural mechanisms that are interactively affected by MTBI. We aim to provide direct evidence that there are long-lasting residual disabilities in subjects suffering from MTBI. We hypothesize that the rate of brain injury symptom resolution predicts the probability of multiple brain injuries in athletes at risk. Our specific aims are: 1) to identify neural mechanisms associated with transient and long-term residual postural abnormalities as a result of single and multiple MTBI;2) to identify abnormal mechanisms associated with neurocognitive deficits, including those specifically involved in postural control in subjects suffering from MTBI;3) to examine destabilizing neural mechanisms in MTBI subjects via manipulations of visual field motion;and, 4) to develop and test unsupervised pattern recognition algorithms for predicting athletes at risk for a single and multiple MTBI. The behavioral, neurocognitive and neural dysfunctions will be tested in student-athletes at risk prior to and after a single and multiple brain injuries using a longitudinal design. A set of tools for assessment of mild traumatic brain injury will be developed based on computer graphics and virtual reality (VR) technologies incorporated with modern human movement analysis and brain imaging (EEG and MRI) techniques. Preliminary research in our laboratory has provided strong evidence for the feasibility of the proposed approach to examine the functional changes in the brain, cognition and balance and to identify athletes at risk for a single and multiple MTBI. Brain damage has been referred to as the "silent epidemic," primarily due to its high level of incidence and the lack of acknowledgement when compared to many other large-scale health issues. In sport and recreational activities alone, there are approximately 300,000 concussions in the United States annually, carrying a $9 to $10-billion price tag for acute care and rehabilitation. In this context, single and multiple concussions are relevant to the study of brain injury in general and in traumatic brain injury in those at risk, such as athletes, as a prototypical example of both short and long-term brain disorders. This project seeks to develop new comprehensive concussion assessment procedures aimed at predicting subjects at risk for concussion and ultimately preventing multiple traumatic brain injuries.